Research Of Sensor Chip Based On Microfluidic And VCSEL Phase-locked Array

Vertical-cavity surface-emitting laser(VCSEL)has the advantages of low threshold,circular light spot,planar process compatibility and easy integration.It has important applications in the fields of optical communication,optical interconnection,and sensing.Multiple VCSEL lasers are closely arranged together to form a VCSEL array.When the distance between adjacent lasers is less than a certain value,the beams of the array will couple,forming a coupled VCSEL array.Beam manipulation of coupled VCSEL array is a current research hotspot.When the phase of the laser array unit changes,its wavefront changes,causing the laser beam to deflect spatially.Therefore,by adjusting the phase difference between the array elements,the laser beam can be manipulated.Based on this characteristic of the coupled array,we propose a liquid refractive index sensor chip based on the coupled VCSEL array,which integrates microchannel structure on the surface of the coupled VCSEL array.The liquid to be measured flows through the microchannel atop the VCSEL array,causing phase difference between the VCSEL array elements,leading to beam deflection.By measuring the deflection angle of the laser beam,the refractive index of the liquid to be measured can be calculated.Thus,the liquid refractive index is detected.The sensor chip combines semiconductor laser technology with microfluidic technology,and has the advantages of real-time,trace and wide detection range.The main research work is summarized as follows:(1)Design of the sensor chip and calculation of key parametersBased on the principle of beam manipulation of coupled VCSEL array,we designed a liquid detection chip.The model was established with FDTD software,and liquid detection characteristics of the chip were calculated when the height of the microchannels was h = 1?m,2?m,4?m,6?m,8?m,10?m,and 24?m,respectively.Experiments show that the higher the micro-channel is,the higher the detection sensitivity of the chip is,but the smaller the refractive index range of the liquid is;on the contrary,the lower the micro-channel is,the lower the detection sensitivity of the chip is,but can detect the liquid in larger range.Therefore,on the premise of ensuring that the chip can detect common liquids(refractive index interval 1.33-1.40),we try to improve the detection sensitivity of the chip,so as to optimize the chip structure.(2)The preparation process of the chipAfter determining the structure of the chip,we design the process flow of chip preparation and draw photoglyphys.The preparation process of the chip is divided into two parts:(a).Preparation of 1×2 coupled VCSEL array;(b).Integration of microfluidic structure on the surface of 1×2 coupled VCSEL array.Through the plasma-enhanced chemical vapor deposition technology,photolithography,sputtering,reactive ion etching,wet etching and bonding and other semiconductor processes,preparation of the chip is completed.Finally,the problems and solutions encountered in the actual device preparation process was summarized.(3)Test of the sensor chip and error analysisFirst,we tested the PIV,near-field,far-field,optical power,and spectral characteristics of the VCSEL coupled array to ensure that the VCSEL array are in-phase coupled.Then,after integrating microchannels on the surface of the VCSEL coupled array,we tested the PIV,far field,optical power and spectrum of the chip to ensure that the subsequent process did not affect the performance of the VCSEL coupled array.We injected liquids such as water,6% sucrose,20% sucrose,isopropanol and 46% sucrose solution into the chip,and measured the deflection angle of the beam,which is 0°,0.60°,1.20°,1.89°,2.41°,respectively,which is basically the same as the theoretical calculation result,proving the feasibility of liquid detection chip.Finally,based on the measured beam deflection angle,we calculated the refractive index of the liquid,compared with the actual refractive index,and analyzed the error of the test results.The average relative error of the chip is 4.4 ‰.It shows that the chip has higher detection performance of liquid refractive index.